Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
So tiny, just 7 by 7 pixels – but still so sexy. Ah yes.
Source Dmitriy Prodchenko
This is the remix of an OCAL clipart called "Rain on Window" uploaded by "pagarmidna".Thanks.This is a seamless pattern of raindrops.
Source Yamachem
Pattern that came out of playing with the 'slinky' plug-in for Paint.net
Source Firkin
A large pattern with funky shapes and form. An original. Sort of origami-ish.
Source Luuk van Baars
Remixed from a drawing in 'Line and form", Walter Crane, 1914.
Source Firkin
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Remixed from a drawing in 'Some account of the Worshipful Company of Ironmongers', John Nicholl, 1866.
Source Firkin
A beautiful dark wood pattern, superbly tiled.
Source Omar Alvarado
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
You may use it as is, or modify it as you like.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 7 No Background
Source GDJ
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Light gray pattern with an almost wall tile-like appearance.
Source Markus Tinner
All good things come in threes, so I give you the third in my little concrete wall series.
Source Atle Mo
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
Zero CC tileable hard cover red book, scanned and made by me. CC0
Source Sojan Janso
Redrawn based on a drawing in 'По Сѣверо-Западу Россіи' Konstantin Sluchevsky, 1897.
Source Firkin
A seamless pale yellow paper background with a pattern of animal tracks.
Source V. Hartikainen
Remixed from a drawing in 'A Girl in Ten Thousand', Elizabeth Meade, 1896.
Source Firkin
This is the remix of "Strawberry Pattern Background" uploaded by "GDJ". Thanks. I realigned strawberries so as to get seamless and changed the BG color.
Source Yamachem
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin